Combat rating system
Combat rating is a mechanic introduced in patch 2.0.1 which are for combat stats on items that were previously percentage based. Rating is converted linearly to percentage; the number of rating points needed to gain one percentage point increases with level and varies depending on the stat, but is the same for all classes. Ratings were introduced because percentage based itemization would have scaled excessively when The Burning Crusade was released and the level cap rose to 70.
Combat rating types
The following combat ratings are currently in use:
Unlike fixed percentages such as 2% critical strike chance, combat ratings diminish in potency as characters increase in level. 2% critical strike chance is the same at every level, while 34 critical strike rating grants 4% crit at level 60, 2.63% crit at level 90, and 0.47% crit at level 120. This allows Blizzard the ability to create and add new and better items to the world without eventually reaching a point where every character has a 100% chance to critically strike.
All classes convert ratings into attributes at the same ratio, with the exception of Mastery, where the ratio is determined by class specialization. Below are the conversions for combat ratings at each expansion's level cap: 
|Rating||Effect||Level 60||Level 70||Level 80||Level 85||Level 90||Level 100||Level 110||Level 120|
|Critical strike||1% critical strike chance[nb 1]||8.5||9.71||11.18||12.02||12.94||15.07||17.62||72|
|Haste||1% haste[nb 2]||8.03||9.17||10.56||11.35||12.22||14.23||16.64||68|
|Mastery||1% Mastery||Varies by specialization - See Mastery for more information|
|Versatility||1% Damage/Healing and 0.5% Incoming Damage Reduction||10.03||11.47||13.2||14.19||15.28||17.79||20.80||85|
Added in Patch 6.0.2, these bonus stats have a chance to appear on gear from the Warlords of Draenor, Legion, and Battle for Azeroth expansions. Some buffs, traits, and player abilities (e.g. ) may grant these stats as well.
|Rating||Effect||Level 90||Level 100||Level 110||Level 120|
|Avoidance||-1% Damage from Area of Effect attacks||5.03||5.86||6.85||28|
|Leech||1% of Damage and Healing returned as Healing||7.19||8.37||9.79||40|
|Speed||1% Increased Movement Speed||3.59||4.19||4.9||20|
These ratings are not typically itemized on current expansion gear and can generally only be found on bonuses like Azerite Traits, or gained passively through other stats. For Parry, a player must have the parry passive skill learned in order to gain any benefit from parry rating. Classes who cannot learn this skill are unable to parry attacks, and will gain no effect from parry rating.
|Rating||Effect||Level 60||Level 70||Level 80||Level 85||Level 90||Level 100||Level 110||Level 120|
|Dodge||1% dodge chance*||9.44||10.79||12.42||13.35||14.38||16.74||19.58||80|
|Parry||1% parry chance*||9.44||10.79||12.42||13.35||14.38||16.74||19.58||80|
*Before diminishing returns.
Removed secondary stats
The following combat ratings are either no longer itemized on gear or have been removed from game. This chart is purely for historical purposes, and will not be updated to reflect future events such as a stat squish.
|Rating||Effect||Level 60||Level 70||Level 80||Level 85||Level 90||Level 90 Squished||Level 100||Patch Removed|
|Armor Penetration||1% Armor Ignored||3.75||5.92||12.31||-||-||-||-||Patch 4.0.1|
|Defense Rating||+1 Defense Skill||1.5||2.37||4.92||-||-||-||-|
|Block Rating||1% block chance||6.9||10.8808||22.6251||88.3594||295.0||-||-|
|Physical hit||1% hit chance[nb 3]||9.37931||14.7905||40.7548||102.446||340.0||-||-||Patch 6.0.2|
|Spell hit||1% spell hit chance[nb 3]||8||12.6154||26.232||102.446||340.0||-||-|
|Expertise||-1% Dodge/Parry and 1% Spell Hit||2.34483||3.69761||7.68869||102.446||340.0||-||-|
|PvP Resilience||-1% Damage from Players||9.292||14.652||30.467||92.316||310.0||12.0||56.0|
|PvP Power||1% Damage/Healing to Players||7.964||12.559||26.115||79.128||265.0||10.0||49.0|
|Multistrike||2 chances to do an extra 30% damage||N/A||N/A||N/A||N/A||N/A||14.0||66.0||Patch 7.0.3|
|Weapon Skill Rating||+1 Weapon Skill (to specific weapon type)||2.5||3.9||-||-||-||-||-||Patch 2.3.0|
- ^ Physical critical strike chance and spell critical strike chance were distinct attributes derived from the same critical strike rating (now equal).
- ^ Haste effects attack speed, casting speed and non-mana resource (e.g. energy, runes) regeneration.
- ^ a b Physical hit chance and spell hit chance were distinct attributes derived from the same hit rating (now retired).
Diminishing returns (no longer relevant)
Avoidance stats suffer from diminishing returns ("DR"), meaning the rate of return for each point contributed from gear is not constant. The in-game tooltips will show the undiminished value, but the amount actually received is lower. Base stats and talents are not affected by DR, but stats from gear are diminished.
The formula to calculate the diminished part of a stat is as follows:
1 1 k — = — + — x' c x
- x' is the avoidance after DR.
- x is the avoidance before DR.
- c is a class-specific cap of the stat.
- k is also a class-specific constant.
The table containing the class-specific caps for parry (Cp) and dodge (Cd) is as follows:
- Patch 7.3.0 (2017-08-29): The Avoidance stat has been reduced in effectiveness by 27% at all levels.
- Patch 7.1.5 (2017-01-10): To allow more options in the gear your character equips, secondary stat ratings (Critical Strike, Haste, Mastery, and Versatility) now contribute less of their respective secondary stat per point.
- This only affects ratings at Level 110.
- Patch 7.0.3 (2016-07-19): Multistrike removed.
- Patch 6.1.0 (2015-02-24): Tertiary Stats for Avoidance, Speed, and Leech now provide about four times as much benefit per stat point.
- Patch 6.0.2 (2014-10-14): Many ratings were removed from the game, including all tank avoidance ratings and hit/expertise. Gear with any of these stats has had them replaced by bonus armor, crit, haste, or mastery. Two new secondary stats were added, multistrike and versatility, which generally only exist on items found in Draenor and later (level 90+ content). PvP ratings are no longer found on any new gear, but old gear still has these stats present. Teritary stats added.
- Patch 4.0.1 (2010-10-12): Mastery rating has been added as a new stat which provides unique benefits for characters based on class and talent specialization. Mastery rating does not currently exist on items in the game, however, Reforging can be used to add Mastery rating as a secondary stat to existing items.
- Patch 3.2.0 (2009-08-04):
- Agility: The amount of agility required per percentage of Dodge has been increased by 15%. This change required recalibrating the amount of dodge a player has with 0 agility by a slight amount as well, so all players will see their dodge percentage vary a small amount.
- Block rating: The amount of bonus block value on all items has been doubled. This does not affect the base block value on shields or block value derived from strength.
- Dodge Rating: The amount of dodge rating required per percentage of dodge has been increased by 15%. This is before diminishing returns. Combined with other changes, this makes dodge rating and Parry rating equally potent before diminishing returns apply.
- Parry Rating: The amount of parry rating required per percentage of parry has been reduced by 8%. This is before diminishing returns. Combined with other changes, this makes dodge rating and parry rating equally potent before diminishing returns apply. Parry still diminishes more quickly than dodge.
- Resilience: No longer reduces the amount of damage done by damage-over-time spells, but instead reduces the amount of all damage done by players by the same proportion. In addition, the amount of resilience needed to reduce critical strike chance, critical strike damage and overall damage has been increased by 15%.
- Armor Penetration Rating: All classes now receive 25% more benefit from Armor Penetration Rating.
- Haste Rating: shamans, paladins, druids, and death knights now receive 30% more melee haste from Haste Rating.
- Hit Rating, Critical Strike Rating, and Haste Rating now modify both melee attacks and spells.
- All items and effects which grant bonuses to spell damage and spell healing are being consolidated into a single stat, Spell Power. This stat will appear with the same values found on items which grant "increased spell damage and healing" such as on typical Mage and Warlock itemization.
- All items have had their bonuses to Weapon Skill Rating converted to a new stat called Weapon Expertise Rating. Each point of Weapon Expertise reduces the chance for your attacks to be Dodged or parried by .25%.
- Healing: Almost all items and enchantments that provide bonus healing now also provide a smaller number (approximately 1/3) of bonus spell damage. There are a few items and enchantments where this was not possible, such as random-stat items and Zul'Gurub enchantments, but this is now the case on virtually all other items.
- Weapon Skill: All items and abilities that granted weapon skill have been changed. In most cases, they were converted to expertise or expertise rating. Ranged attacks do not benefit from expertise, so ranged weapon skill has generally been replaced by critical strike bonuses or hit bonuses. In a few cases, talents have been changed to other effects to avoid granting players excessive amounts of expertise.
- Resilience rating: The reduction to the percent chance to get a critical strike now also reduces the damage dealt by damage over time effects by the same percentage.
- Spell Haste: The amount of spell haste rating needed per percentage of haste has been increased substantially. However, spell haste will now affect channeled spells, increasing the rate of their effects and decreasing their total duration. The same amount of damage/healing per casting will occur, but will take less time.
- The amount of parry rating needed to get 1% parry has been reduced by 25%.
- Dodge Rating: Low level players now calculate dodge from dodge rating at the same rate as level 34 players.
- New item property "Resilience" has been introduced. Resilience reduces your chance to be the victim of a critical strike, and reduces the amount of damage critical strikes do to you.
- Weapon Skill now does the following:
- Weapon skill will no longer reduce the percentage damage lost due to glancing.
- The player will gain 0.1% to their critical strike rating per weapon skill against monsters above their level.
- Items that give bonuses, such as critical strike percentage, have been modified to adhere to a combat rating system.
- All current items will provide the exact same benefit from ratings at level 60 as they provided before the ratings system.